Download Extra Notes on IPv4 Addressing

IPv4 ADDRESSING and PACKET
STRUCTURE
IPv4
• Internet Protocol addressing version 4 (IPv4) is the
basis of Internet.
• Every connected host has a four octet address
expressed in decimal:
AAA.BBB.CCC.DDD
For example: 66.102.7.104 (Google)
• A host can send a packet to an IP address and it will be
delivered to the correct destination.
CLASSFUL ADDRESSING
• Under IPv4 addressing scheme (classful
addressing), the class of the network may be A, B
or C. The class effects how the four number IP
address is intrepreted. For all classes, the last
byte is limited between: 1 – 254
- 0: reserved for network address
- 255: reserved for broadcast address
Network
Address
Host
Address
Host
Address
Host
Address
B
Network
Address
Network
Address
Host
Address
Host
Address
C
Network
Address
Network
Address
Network
Address
Host
Address
A
• CLASS A (large network): the first byte identifies the network and
the last 3 bytes represent an address range for hosts on the
network.
Byte 1: 1 – 126
Byte 2 and 3: 0 – 255
No. of hosts (max): 16,646,144
• CLASS B (medium network): the first two bytes identify the
network and the last 2 bytes represent an address for hosts on the
network.
Byte 1: 128 – 191
Byte 2 and 3: 0 – 255
No. of hosts (max): 65,024
• CLASS C (small network): the first three bytes identify network and
the last byte represent an address for hosts on the network.
Byte 1: 192 – 223
Byte 2 and 3: 0 – 255
No. of hosts (max): 254 hosts
• CLASS D: Byte 1: 224 – 239
• CLASS E: Byte 1: 240 – 255
• Broadcast Address: broadcast address is
intended to go to every host on the network.
(host address bytes are replaced with 255 (all
ones)
Example: Class B network with a network
address of 174.148.0.0 would have a
broadcast address of 174.148.255.255
• Network Address: is formed by replacing all host bytes
with 0.
Example: Class B IP address of 174.148.10.5, has
network address of 174.148.0.0
• Network Mask (netmask): a host must know if a
received packet relates to the network to which the
host is a member. Membership of a network is
determined using netmask defined on every network
host.
netmask = all network bits set to 1, all hosts bits
set to 0
Example: Class A = 255.0.0.0, Class B = 255.255.0.0
5 Different Classes of IP Address
CLASS A
1.0.0.0 to 127.255.255.255
CLASS B
128.0.0.0 to 191.255.255.255
CLASS C
192.0.0.0 to 223.255.255.255
CLASS D
224.0.0.0 to 239.255.255.255
CLASS E
240.0.0.0 to 255.255.255.255
PRIVATE IP ADDRESS
(are not used anywhere on public
internet, reserved for private LANs)
Network
Class
Network Numbers
Network Mask
No. of Networks
No. of Hosts per
Network
126
16,646,144
16,383
65,024
CLASS A
10.0.0.0
255.0.0.0
CLASS B
172.16.0.0 to
172.31.0.0
255.255.0.0
CLASS C
192.168.0.0 to
192.168.255.255
255.255.255.0
2,097,151
254
255.255.255.0
-
-
LOOPBACK 127.0.0.0 to
(localhost) 127.0.0.7